When ducts are aligned and fixed to one another, a sound structural joint can be achieved with several known types of couplings. However, as is often the case, when ducts are misaligned, these known couplings are difficult to assemble and require excessive force to prevent leakage. This force often causes fatigue failures in service.
In order to overcome the deficiencies of the prior, known couplings, the inventor of the present invention disclosed in U.S. Pat. No. 4,436,326, assigned to the assignee of the present invention, a flexible coupling that is adjustable to accommodate misalignment of ducts to be connected in any one or any combination of three basic directions, viz. axial, radial, and angular. The coupling also permits conical flexibility to a substantial degree, i.e, on the order of about .+-.3.degree. to about .+-.4.degree.. This flexibility, the angular movement of the ducts relative to one another within the assembled coupling, is provided to permit float between ducts relative to one another to compensate for attaching structural deflections.
A typical example of such deflections is the movement of an aircraft wing and/or engine in flight. Thus, the flexibility of the above-noted coupling permits movement between connected ducts, such as fuel and hydraulic lines or ducts, when the aircraft is in operation thereby eliminating the buildup of stresses which can result in leakages and structural failures.
While operationally quite efficient, this coupling necessitated the incorporation of either four or five elastomeric seals, thus increasing the opportunity for leakage. Additionally, the assembly of this coupling is somewhat complicated increasing the probability of incorrect assemblage of parts.